The present invention generally relates to wood chippers and specifically relates to controls for wood chipper infeed conveyor systems, as are typically found on large wood chipping machines.
Wood chippers are large, heavy machines and are commonly built with an integrated trailer towing frame for portability to a job site. An infeed chute with a powered conveyor is often used to feed wood stock, typically a tree, into the chipper. These infeed conveyors typically use chains, rollers or combinations of both to feed the material into the front side of a cutter disk. The cutter disk is commonly a thick, circular metal plate with at least a pair of cutter knives which are mounted adjacent chip slots, formed in the disk. The disk is rotatably mounted in a cylindrical chamber and rotated at a relatively high speed by a motor, also commonly mounted on the integrated frame. The disk is often set at an acute angle to the direction of feed such that the knives tend to draw the material into the disk. As the material is feed into the front side of the disk, the knives continuously slice the end of the material to form chips which pass through the chip slots to the back of the disk. The chips are removed from the back of the disk in part by centripetal force and in part by an air flow which is induced by fan blades, commonly mounted on the back of the disk. A chip discharge chute extends tangentially from the disk housing and the air flow from the fan blades carries the chips out of the housing and through the chute for discharge from the chipper.
The conveyor system will often have at least a lower powered rollers rotatably mounted to the infeed chute frame and rotating at a predetermined speed for controlled infeed of material into the cutter disk. An upper powered infeed roller is also provided such that material is captured between the upper and lower rollers for positive feed of the material without slippage. A wide range of material sizes can be feed into the chipper and is usually accommodated by a floating upper roller, rotatably mounted on a pivotable carrier. A double acting hydraulic ram is commonly connected between the chute frame and the pivotable upper roller carrier for pulling the upper roller down towards the lower rollers to grab material between the upper and lower rollers or for lifting the upper roller away from the lower rollers to accommodate large material or to clear a material jam. Usually, the hydraulic ram is manually controlled for lifting the upper feed roller or pulling it down. In the normal float mode, the upper feed roller will roll on top of small to medium sized materials. However, when large materials are fed in, the upper feed roller can jam and stop turning. As is currently customary when an infeed jam occurs, an operator who monitors the infeed of material, actuates a manual control to lift the upper feed roller and clear the jam.
A wood chipper is often used in a contemporary wood chip processing operation by placing it between a debarking apparatus and a chip receptacle. Trees are dragged out of the forest to the operation cite where a small crane apparatus feeds the trees through the debarker and into the chipper. The chipper conveyor system receives the trees out of the debarker apparatus and feeds them into the chipper disk where they are cut into chips and the chips are discharged into the receptacle. While one operator is required for operating the crane device to feed trees through the debarker and into the chipper, a second operator is required to monitor the infeed of trees into the chipper and to manually lift the upper infeed roller to accommodate large trees or to clear infeed jams. This second operator is not otherwise required for the safe and effective operation of the wood chip production site.